Producing fresh water from air raised to high humidity by exposure to water vapor from contaminated sources of water



Aug. 1, 1967 c. DOBELL 3,334,026 PRODUCING FRESH WATER FROM AIR RAISEDTO HIGH HUMIDITY BY EXPOSURE TO WATER VAPOR FROM CONTAMINATED SOURCES OFWATER Filed Oct. 25, 1963 5 Sheets-Sheet 1 2nd STAGE wmo DIRECILION*Is1STAGE- WICK I5 24 so 30 A 30 FIXED RUDDER :5! CONDENSATE TANK COOLERI3 I? 32 I3 25 I CONDENSATE PUMP 3rd STAGE 2nd STAGE BALLAST TUBE OFFLOAT INVENTOR Curzon Babe/l ATTORNEYIS Aug. 1, 1967 c. DOBELL 3,334,026

PRODUCING FRESH WATER FROM AIR RAISED TO HIGH HUMIDITY BY EXPOSURE TOWATER VAPOR FROM CONTAMINATED SOURCES OF WATER Filed Oct. 25. 1963 3Sheets-Sheet 62 FIXED RUDDER ./-58-TRANSPARENT I 64 v r SEA WATER ,4s'r-soLAn HEAT ABSORBING TROUGH Z PINS z5| L 3 i 4 v 72 J COOLANT f50-ROTATES r3 r-CONDENSER EXHAUST AIR 53 55 k DRY RAM AIR is 4-L 54 I II Q CONDENSj-ITE' m-HEATER re o l 1 59 Curzon Dobel/ ATTORNEYS Aug. 1,1967 c. DOBELL 3,334,026

PRODUCING FRESH WATER FROM AIR RAISED TO HIGH HUMIDITY BY EXPOSURE TOWATER VAPOR FROM CONTAMINATED SOURCES OF WATER Filed Oct. 25 1963 I 5Sheets-Sheet 99 I a9 1 3rd, Stage 2nd. Si0ge lst Stage Product WaferTank INVENTOR Curzon Dabs/l ATTORNEZS United States Patent 3,334,026PRODUCING FRESH WATER FROM AIR RAISED TO HIGH HUMIDITY BY EXPOSURE TOWATER A VAPOR FROM CONTAMINATED SOURCES OF WATER Curzon Dobell, P.O. Box643, Nassau, Bahamas Filed Oct. 25, 1963, Ser. No. 319,058 12 Claims.(CL 203-) The present invention relates to a method and apparatus forthe production of potable or fresh water and more particularly to theabstraction of said potable water from humid air in a three stage cycleor apparatus.

It is well known that in certain areas of the world there is a shortageof fresh water, and particularly potable water because of thegeographical nature of the area or due to the fact that certain areasalthough they have had a sufficient water supply up to the present timenow require more fresh water because of population and industrialexpansion.

Some common methods of abstracting fresh water from sea water orbrackish water have been directed toward such abstraction by freezing orelectrolysis.

In accordance with the present invention it is an object hereof toproduce potable or fresh water in a three stage process by passing astream of atmospheric air which contains a large quantity of water vaporthrough a first stage wherein the temperature of the air is increased sothat the saturation point of the air increases as a result of which agiven volume of air will absorb a greater quantity of water, in the formof vapor and hence it can carry more water vapor therein. After thetemperature of the air stream is increased it is exposed to a source ofmoisture in a second stage which it can absorb like a sponge until itreaches the saturation point. Thereafter, this stream of air is passedto a third stage wherein the air temperature is lowered to cool thesaturated air, and to condensate the water vapor in the air and thusproduce fresh or potable water.

It is another object of the present invention to provide a method andapparatus for producing fresh water from a flowing body or stream ofatmospheric air, in which the fresh water is produced in a three stageprocess using predetermined differentials in temperature and pressure bypassing the stream of air through the first stage and increasing itstemperature while decreasing its pressure so as to increase the amountof water vapor that can be absorbed by the stream, passing it through asecond stage and increasing the actual water vapor carried in the airstream by exposing it to additional water vapor and thereafter passingit to a third stage wherein the temperature of the air is decreased andthe pressure is increased so as to squeeze out and condense the watervapor in the air stream.

It is another object of the present invention to provide an apparatusfor producing fresh watercomprising three stages in the form of twoconcentric cylinders vertically disposed to provide a chimney effect tomove increased quantities of air containing water vapor therethrough andwherein the airvstrearn moves upwardly in the first and downwardly inthe third stage. The first stage is provided with means for increasingthe temperature of the air flowing therethrough. The first stage isprovided with fin members and the entire surface is painted a dull blackto absorb solar heat and the third stage is insulated therefrom. andexposed surfaces are painted a shiny white to minimize heat absorptionin the third stage. The provision of the means for heating the air inthe first stage will cause the incoming air to rise. The second stage isprovided with means for increasing the vapor content of the air flowingtherethrough. The third stage is provided with cooling means which willcause the air stream to move downwardly or sink thereby creating anormal draft through the three stage apparatus irrespective of the windvelocity.

It is another object of the present invention to provide an apparatusfor producing fresh water from a stream of air caused to fiowtherethrough, such apparatus having concentric vertically disposedcylindrical members forming a first stage, a second stage, and a thirdstage, and in which the entire apparatus is provided with means forpermitting it to rotate'ou a swivel base whereby the air intake to thefirst stage is pointed into the wind and the exhaust from the thirdstage is pointed away from the wind.

It is another object of the present invention to provide an apparatusfor the production of fresh water consisting of three separate stages tothe form of the concentric cylinders standing vertically to provide achimney effect to move increasing quantities of air and in which thefirst stage is provided with auxiliary heater means so as to increasethe temperature of air in the first stage when the solar temperaturedifferential falls below a predetermined level, and having auxiliary fanmeans disposed in the third stage to move the air and increase itspressure therein when the wind velocity falls below a predeterminedlevel.

The cross sectional area of the first stage can be smaller than that ofthe third stage so as to provide reduced pressure in the first stage andincreased pressure in the third stage.

It is another object of the present invention to provide apparatus forthe production of fresh water from a stream of atmospheric air passedtherethrough and processed in a first, second and third stage in theform of concentric cylinders standing substantially vertically toprovide a chimney effect to move increased quantities of air, whereinthe air in the first stage can be heated 'by solar energy and the airstream can be cooled in the third stage to squeeze the water vapor outof the air without the use or operation of a fan between the first andthird stages and without the use of auxiliary heater means when thesolar temperature is above a predetermined level and the wind velocityis above a predetermined level, so that the only energy required is forrunning the cooling water and condensate pumps for removing condensateextracted from the air stream.

It is another object of the present invention to provide an apparatusfor the production of fresh water having a first, second and third stageincluded therein, and a structure which permits the apparatus to floatin the water or to be utilized on land.

It is another object of the present invention to provide an apparatusfor the production of fresh water comprising a first stage consisting ofan air inlet duct and means for utilizing solar energy to heat the airpassing through the first stage, and a second stage including areservoir and wick means therein for containing water to charge the airstream with the maximum amount of water vapor it is capable ofabsorbing. The pressure can be reduced in the first stage by the Venturimethod and/ or use of a pressure fan placed between the second stage anda third stage with a restricted outlet. The temperature of the air isreduced in the third stage and the pressure increased in the third stagein order to squeeze out in the third stage by cooling and pressure thewater vapor contained in the flowing stream of air.

It is another object of the present invention to provide an apparatus ofcompact arrangement and which is made out of light gauge sheet metalwith a structure that enaibles it to be placed on land at one time to beutilized to produce fresh water, and to be floated in sea water atanother time with the first and second stages disposed above the sealevel, and the third stage disposed below the sea level to provide atemperature differential between the first stage and the third stage.

It is another object of the present invention to provide an apparatusfor the production of fresh water consisting of three stages havingsubstantially a ring or loop configuration with the first and secondstages consisting of a relatively wide rectangular horizontal air flowduct of shallow depth, which thereafter is curved or looped downwardlyand reverses its direction providing another horizontally extendingsection, and which duct thereafter loops or curves upwardly andterminates in a short forwardly extending horizontal outlet portion. Thesecond stage is provided with means for adding water vapor to the airstream and a pressure fan is provided at the downstream side of thesecond stage. The third stage is provided with cooling coil means so asto decrease the temperature of the saturated air flowing through thethird stage in order to condense out and remove the saturated watervapor from the air stream, and which cooling coil means can be providedwith a connection for supplying heated water to the second stage so thatthe humidity of the air flowing through the first stage can be decreasedin order to increase the efficiency of the fresh water production.

It is another object of the present invention to provide a three stagefresh water production apparatus consisting of a looped duct with fanmeans disposed between the second stage and the third stage of theapparatus, and a cooling coil in the third stage through which unitwater can be pumped to cool the saturated air and squeeze out of it thewater vapor therein, and in which the condensate from the air stream iscollected in the bottom of the third stage and can be pumped to a smallstorage tank disposed in the apparatus at a higher level. The apparatusis also provided with rudder means and flotation means thereon so thatthe air inlet to the first stage is always pointing into the wind, sothat when the wind velocity is above approximately ten miles an hour,there is no need to run the fan means between the second and thirdstages and the only energy required in the apparatus is to run the smallcooling water and condensate pumps.

It is another object of the present invention to provide a loopedconfiguration for the production of fresh water from a stream ofrelatively humid air passed through the duct, with a first stageprovided with baffle means for utilizing solar energy to increase thetemperature of the air flowing through the first stage, and reservoirand wick plate means disposed in the second stage through which thestream of air passes so the air will absorb water and increase its watervapor content, and a third stage in communication with the first andsecond stages to receive the saturated and humid air stream therefromwith fan means disposed between the second and third stages with arestricted inlet to reduce the pressure in the first and second stagesand increase the pressure in the third stage, and cooling means in thethird stage so that the decrease in the temperature and increase inpressure of the air stream as it flows through the third stage permitsthe water vapor carried in the air stream to condense out into freshwater.

It is yet another object of the present invention to provide a freshwater apparatus consisting of three stages to produce fresh water byremoving the wick plate means in the second stage and cooling the tubesor coil in the third stage, and disposing the first and second stagesabove the ground level to increase the incoming air stream temperature,and disposing the third stage below the ground or otherwise insulatingit to provide some degree of cooling plus increasing the pressure in thethird stage by the fan so that some pure water can be produced by thethird stage alone.

Other features and advantages of the present invention will be readilyapparent from the following detailed description when considered inconnection with the accompanying drawings forming a part hereof and inwhich:

FIGURE 1 is a side view of the method of carrying out my invention andan apparatus embodying the invention;

FIGURE 2 is a front end view of the apparatus shown in FIGURE 1, lookingat it from the left side;

FIGURE 3 is a side elevation view of the method of my invention, andanother apparatus embodying the invention;

FIGURE 4 is a horizontal section of the apparatus taken along line 44 ofFIGURE 3; and

FIGURE 5 is a side view of still another apparatus for carrying out thepresent invention.

Referring to the drawings, the reference numeral 10 generally designatesan apparatus or structure for the production of freshwater from arelatively humid stream of air which contains a large quantity of watervapor passed through the structure to a three-stage operation. Thestructure 10 is substantially rectangular in shape as best illustratedin FIGURE 2 and is provided with a frame made of vertical legs ormembers 11 spaced laterally and longitudinally of each other to whichhorizontal or transversely extending members 12 and 13 are secured byany suitable means such as brazing or bolts and the like to form a rigidstructure. Although the drawings illustrate only two sets of verticalmembers 11 and two sets of transverse members 12 and 13, it is apparentthat if desired more structural members can be provided.

The air flow duct generally designated 14 through which the air streamof atmospheric air flows consists of an upper elongated fiathorizontally extending portion or section 15, a downwardly curvedsection 16, a lower straight horizontal section 17, and an upwardlycurved section 18. The air duct 14 comprises a generally loopedconfiguration with the portion 16 curved backwardly upon itself, and thedischarge section or portion 18 curved backwardly or rearwardly bentwith respect to the straight section 17. The discharge section 18 isdisposed just below the portion 15 of the duct and extends inwardlythereof, so that the portion 15 overlaps the backwardly curved portion18 as best shown in FIGURE 1. The inlet end 19 of the duct is slightlyenlarged when compared with the section 15 of the duct which comprises ashallow box approximately three inches deep and six feet wide. Thebottom of section 15 of the duct includes a reservoir 20 adapted tocontain approximately one-half to one inch of sea water, or contaminatedwater, which saturates a plurality of spaced vertical wick plates ormembers 22 disposed adjacent the discharge and of the section 15. Itshould be noted that any overflow of water in reservoir 20 will spillover the end or lip 31 of inlet end 19 and duct 14. The wick plates 22extend across the air passage formed by the section 15 and are generallyof a braided cotton material so that water from the reservoir 20 willcompletely saturate them. They can be properly secured within the ductsection 15 by any suitable means. The duct 15 is curved or bent upwardlyas indicated at 23 adjacent the discharge end so that any of the waterin the reservoir 20 will not overflow into the curved section 16 of theair duct.

The first stage of the apparatus is generally indicated at 24 andconsists of the portion of the duct section 15 from the inlet end 19 toa point 15a disposed along section 15. The second stage of the apparatusextends from 15a and includes section 16 to a point approximatelyadjacent the fan 25 located at the discharge end of the duct section 16.The duct 14 progressively has its cross section reduced or narrowed fromthe wide shallow box configuration of section 15 with a cross section ofapproximately one and a half square feet to an intermediate crosssection adjacent 16 of approximately one square foot until it finally isreduced or necked to its smallest cross section beyond the fan 25 insection 17 of the duct. Section 17 constitutes the third stage of theapparatus.

The first and second stages adjacent the section 15 and beyond point 15aof the duct are provided with a plurality of vertical transverselyextending elongated baffle plates 30 properly secured thereto andpainted black, as is the duct 15, so that a relatively large blacksurface area is exposed to the sun for heating the air. Heat can also besupplied to the first stage by conventional means with an oil or gasheater so as to increase the temperature of the stream of humid airflowing through the first stage of the device.

In stage one the temperature of the air stream through the apparatus isincreased and the pressure may also be decreased. Both changes increasethe saturation point of the air so that it can carry more water vapor.Actually the increase oftemperature is far more beneficial. Increasingthe temperature requires only a small amount of the energy which wouldbe required to increase the saturation point to the same level bydecreasing the pressure. It is not necessary to have both increase intemperature and decrease in pressure.

After stage one where the air is put in a condition where it can absorbmore moisture, it then passes to stage two where it is exposed to asource of moisture which can be sea water or brackish-water from wellsor any other source of polluted water unfit for human consumption orindustrial requirements. Exposing the air to an additional source ofmoisture is done by using wick plates 22 in which the moisture can riseby capillary action where it intercepts the air flow, or by the use offog nozzles directed against the air flow in a closed chamber. In eithercase provision can be made that no drippage from the wick plates orcondensation from the fog nozzles is carried into the third stage tocontaminate the product water. This can be done by a drip pan in thesecond stage draining in the opposite direction of the air flow.

In the third stage the air can be cooled in several ways such as bycirculating the contaminated water through cooling coils if thetemperature of this water is F. or more below the temperature of the airstream, or by circulating the product water through cooling coils if itis 10 F. or more below the temperature of the air stream, or bymechanical refrigeration by circulating condensed Freon gas throughcooling vcoils just as in a room air conditioner, and discharging theabsorber heat to the outside an.

The third stage is provided with a cooling coil having parallel passes32 and 33 in communication with a condensate pump 34 for passing coolingwater through section 17 of the third stage of the air duct to reducethe temperature of the air flowing therethrough in order to condense andsqueeze out from the saturated air the water vapor therein to producefresh water. The two passes 32 and 33 of the cooling coil discharge intoa relatively large diameter tube 35 closed at both ends and incommunication with a pipe connection 36 for supplying feed water to thereservoir 20 in section of the first stage of the ap paratus. Theutilization of the cooling water from the two cooling coil passesincreases the temperature of the feed water before it is supplied to thereservoir and thus increases the efliciency of the device. The coolingwater passed through the cooling coils 32 and 33 can be from a sourcesuch as a well, or sea water as illustrated in FIGURE 1.

I In the embodiment illustrated in FIGURE 1, the device is provided withstabilizers 38 in the form of sealed ballast members or tubes, as bestshown in FIGURE 2', properly connected to opposite sides of thestructural members 11 so that the device will float in sea water. Thelevel of the sea will be -as indicated at 39 in FIGURE 1 with the sealevel being disposed at approximately one-half the height of the device.When the device is floated in the sea, the lower half of the section 16and 18 and the section 17 are completely submerged in the sea water, asillustrated, to properly cool the thirdstage .of the operation and.decrease the temperature of the air flowing therethrough. When thisdevice is used on land, the bottom of members 11 may be disposed on theground or, if desired, thelower portion of the device can be properlyinsulated and placed.

below ground level so that the apparatus is half underground andanalogous to its disposition in sea water.

A condensate extraction trough or channel 40 extends below the coolingcoils 32 and 33 and below the lower end of the duct 17 so thatcondensate from around the outside of the walls will fall to the bottomof the duct and into the trough or channel 40. A condensate pipe 41communicates with the trough 40 and with the suction of a condensatepump 42 properly secured by any suitable means to the lower side of theduct section 15. The condensate pump 42 is provided with a dischargeline 43 for passing the purified water into a storage tank 44 properlysecured to the structural members 11. The tank 44 extends transverselyof the structure between the sealed ballast members or tubes 38.

A vertical fixed fin or rudder 45 is properly secured by any suitablemeans to the upper surface of the duct portion 16 and anchor connectionmeans 46 are properly secured to the bottom of the duct section 18 sothat an anchor can be attached to the device. The rudder 45 permits thedevice to head into the wind in boat fashion so that the inlet 19 forreceiving the incoming air is constantly facing into the wind. Theoutlet 46 at the discharge end of the duct section 18 is disposed in adirection facing opposite the direction of the inlet 19 and is thereforeconstantly facing away from the wind.

The differential in pressure between the first stage and the third stageis accomplished by making the cross-sectional area of the first stagelarger than the cross-sectional area of the third stage so that thevelocity of a given volume of air through the first stage will be lowerthan through the third stage, which will produce a higher pressure inthe first stage than in the third stage. By reducing the air intake andexhaust openings the use of a fan located between the first and thirdstages will also reduce pressure in the first stage and increase it inthe third stage.

In operation, for producing fresh water from a stream of air having afairly high relative humidity, the air enters the inlet 19, when thedevice is floated in sea water, as shown in FIGURE 1, and passes orflows through the air duct section 15. The sea water flows into thereservoir 20 through the pipe line 36 from the cooling coils 32 and 33.The water in the reservoir 20 rises by capillary action up through thewick plates 22 and the air stream intercepts and passes through thebraided cotton members to charge the air with the maximum amount ofwater it is capable of absorbing. The duct and battle plates 30 whichare painted black and exposed to solar radiation heat and increase thetemperature of the air stream flowing through the first stage section 15of the device. The provision of the fan 25 supported on spider meansadjacent the inlet and of thethird stage section 17 causes a pressuredifferential between the first stage 34 and the third stage with thefirst stage having a reduced pressure and the third stage having anincrease in pressure.

In the first stage the temperature of the air stream is increased andthe pressure is reduced. The saturation point of the air streamincreases so that a given volume of air will'absorb a greater quantityof water in the form of invisible vapor. Thereafter, the air stream hasthe amount of water vapor carried in it increased by passing it to thesecond stage wherein it is exposed to a source of moisture.

In the third stage the air stream has its pressure increased and itstemperature reduced so that the dew point of the air stream'is decreasedand the water vapor carried in the air stream begins to condense ordeposit out as a liquid with the water particles or droplets falling tothe bottom of the duct section 17 and being caught in the condensateextraction channel 40 after which they are pumped by the condensate pump42 through line 41 into the fresh water storage tank 44.

In 'warm climates with a fairly high relative humidity, it has beenfound the air contains a large quantity of water vapor which can beabstracted with far less energy than it takes to get the water out ofthe salt from sea water.

At 70 F. temperature and 70% relative humidity, one cubic mile of aircontains 26 million gallons of water. Thus some pure water can beproduced by the third stage alone, i.e., by condensing the water out ofthe air by pressure and cooling and using a fan when necessary tomaintain the air flow. If a source of salt or brackish water isavailable, the efficiency can be greatly increased by adding to thispressure and cooling stage a first stage in which the incoming air israised in temperature and a second stage in which the air stream isexposed to the salt or brackish water. This increases the amount ofwater vapor in the air which is squeezed out in the third stage bycooling and pressure.

When the wind is miles an hour or more, there is no need to run the fanand the only energy required is to run the small cooling water andcondensate pumps. When the wind velocity is below 10 miles and hour, thefan is automatically turned on to continue the same flow of air throughthe machine.

It has been found by calculations that with the sun shining, an airtemperature of 80 F., 70% relative humidity, cooling water temperatureat, 75 F., and a wind velocity of 10 mph, this pressure and coolingstage alone will produce 2.5 gallons of Water per hour with an energyconsumption of 0.3 kw.h. If the wind velocity falls below 10 m.p.h., thefan cuts in using an additional 0.03 kw.h. At two cents per kw.h., theenergy, including the fan, would be $0.48 (forty-eight cents) per 1,000gallons of water.

It would also be possible to produce water by this device in areas farremoved from any source of salt or brackish water. In this case the wickplates and the cooling tubes would be removed. The first stage would beexposed above ground to heat the incoming air and the third stage wouldbe set below ground or otherwise insulated to provide some degree ofcooling, plus pressure by the fan.

FIGURES 3 and 4 illustrate a modification of the apparatus for carryingout the method of the present invention. This embodiment comprises astructure 50 having an outer cylindrical member 51 within which isdisposed an inner cylindrical member or tube 52. The cylindrical member51 is sealed or closed oil at the top and bottom and is provided with anair inlet duct or conduit 53 in the lower end thereof through which arelatively humid stream of air is passed. The inner cylindrical memberor tube 52 is open at the upper end and is provided with a curved orbent section 54 adjacent its lower end extending through the wall of thecylindrical member 51 so as to form a discharge or outlet opening 55 forthe apparatus. The tube 52 is concentrically disposed within thecylindrical member 51 so that an annular passage 56 is provided aroundthe tube 52. It is. thus apparent that the cylindrical member 51 and thetube '52 form parallel cylinders standing vertically to provide achimney eifect to move increased quantities of air through thestructure. A plurality of annular or thin ring baflle plates or fins 57are properly secured by any suitable means to the outer surface of thecylindrical member 51 to absorb solar heat. A cylindrical casing orhousing 58 made of transparent plastic material is properly secured byany suitable means over the fins 57 to reduce solar heat loss due towind. The heating fins are painted black to absorb more heat. The fins57 as can be clearly seen in FIG. 3 are stacked in a verticalarrangement around the cylindrical member 51.

The bottom 59 of the cylindrical member 51 is mounted by any suitablemeans on a bearing 60 which in turn is mounted on a fixed pedestal 61 sothat the entire structure can freely rotate or swing around the base 61.A rudder 62 is properly secured to the upper end of the cylindricalmember 51 and extends through the plastic casing so that the intake 53is pointed into the wind and the exhaust or discharge outlet 55 which isdisposed opposite the intake 53, is pointed away from the wind.

An annular trough or liquid reservoir 63 is secured to the outer surfaceof the inner cylindrical member 52 adjacent the upper portion thereofand in annular passage 58. Water is supplied to the reservoir 63 byinlet tubing or piping 64 extending through the cylindrical member 61and the plastic casing. The tubing 64 is made of flexible material andis of such a length that it will not interfere with the rotation orswiveling of the structure. Wick plates 65 of braided cotton or otherwicking material are disposed in the trough 63 and extend across theupper portion of the annular passage 56 so that the incoming stream ofair flowing through the structure is exposed to a source of water tocharge the air with the maximum amount of water it is capable ofabsorbing.

The first stage of the structure comprises the portion of annularpassage or chamber 56 below and up to reservoir 63. The portion ofchamber 56 adjacent and above 63 and passage 66 adjacent the upperportion of the tubular member 52, and extending down to the pressure fan67 comprises the second stage of the structure. Fan 67 is secured by aspider member 68 within the tubular member 52.

The first stage is also provided with an auxiliary oil, gas or electricheater 70 disposed adjacent the intake 53 which can be operated byautomatic means if desired when the solar temperature differential fallsbelow a predetermined level.

The third stage of the structure comprises the portion of tubular member52 disposed below the fan 67. The third stage is provided with a coolingcoil 71 having inlet and outlet cooling pipe lines 72 and 73respectively. The lines 72 and 73 are made of flexible material and areof sufiicient length so as to permit the entire structure to rotate orswivel about the base 61 without causing any damage to the lines 72 and73. A condensate reservoir or trough 75 is disposed in the bottom of theduct section 54 and is provided with a condensate discharge line 76connected thereto by any suitable means, in communication with a storagetank, not shown.

The cooling water entering line 72 and flowing into the cooling coil 71can be connected to a source of contaminated or brackish water or can beconnected to the fresh water storage tank, not shown. The supply ofwater to the reservoir 63 through the line 64 can be from any moisturesource such as sea water or other contaminated or brackish water.

In operation, a stream of relatively humid air containing a largequantity of water vapor passes through the inlet 53 into the first stageof the structure and thereafter flows upwardly through the annularpassage 56, changes direction, and flows downwardly through the tubularmember 52. The increase of temperature in the flowing through the firststage and through the annular passage 56 provides a natural updraftsince warm air rises. As the body or stream of air passes through thesecond stage, wick plates 65, and is exposed to a source of water theair is charged with the maximum amount of water it is capable ofabsorbing.

The clear plastic cylinder prevents any solar heat loss due to windwhile the fins 57, which are painted black, absorb a maximum amount ofsolar radiation to heat the air stream. So long as there is a sufiicientwind and the sun is not completely obscured and a supply of brackish orotherwise polluted water is available, the structure when rotatable willproduce potable water with the use of a very small pump to circulate thefeed and cooling water.

The pressure fan 67 between the second and third stages can be actuatedby a switch if desired to cut in the fan whenever the wind drops below acertain speed or it can be run continuously for a higher production. Theoil or gas heater 70 disposed to the intake 53 can cut in whenever thetemperature drops below a certain value or it can be used continuouslyif desired to supplement the solar heat. To provide a 24-hour productionof water the water would operate during the hours of darkness or heavyclouds and the fan would operate when the wind velocity 9. drops belowapproximately 8to 10 miles an hour. If desired the structure can'operate in regions far removed from any source of feed water by usingstandard refrigeration equipment to provide the difierential intemperature between the first and third stages, and the use of a fan toproduce the required volume of air flow. The efliciency would thendepend entirely on the relative-humidity of the air. 7 r p The airstream flows into the top 66 of the tubular member 52 and thereafterdownwardly therein. The heating of the air in the first stage of thestructure and the decrease of the temperature by the cooling coil 71 inthe third stage will cause the air to rise and sink in the cylinders,respectively, thereby creating a normal draft in the structureirrespective of wind velocity.

Thus the structure of the invention embodied in FIGS; 3 and 4 provides athree stage device for carrying out the method of the present inventionin the form of parallel cylinders which stand vertically to provide anatural chimney effect to promote the air circulation therethrough andthe production of fresh water.

Accordingly, the present invention provides a method of producing freshwater from a contaminated source or sea water in a three stage operationin which the temperature of a relatively humid stream of air has itstemperature raised in the first stage and, if desired, its pressuredecreased in the first stage, and thereafter the air passes to thesecond stage wherein it absorbs moisture, after which the stream of airgoes through a third stage and has its temperature lowered, and itspressure increased if desired in order to squeeze out or condense thewater vapor in the stream of air to potable water.

In addition the present. invention provides a method of utilizing theabove described three stage operation wherein the fairly high relativehumidity of a stream. of air containing a large quantity of water vaporcan be abstracted with far less energy than it takes toget the water outof the salt in sea Water:

Finally, the present invention further provides a method of producingfresh or potable water in a three stage operation using predetermineddifferentials ,in tempera ture and pressure.

Referring to the modification of the invention shown in FIGURE 5, itembodies the same three stage principle for producing fresh water,i'asalready described except it operates entirely on purchased energy toheat the air in the first stage and reduce the temperature in the thirdstage, plus a blowcrfan tomaintain .constant circulation. In thisarrangement no'use' is made'jof solar heat or wind velocityiwhile thiswould cost more to operate, a larger production. of. pure water can beaccomplished with a much-smaller. machine. y y l v L Iii-thisembodiment, .a casing 80- is provided having a firststage with an airinlet 82 and an electric heater 84 thereto. The air outlet 86 from thefirst stagecommunicates -with.the.second stage. provided with'a sprayheader 88 having a plurality of spray nozzles forspraying water dropletsacross the path of flow of the-air stream. A' drip conduit 89 isprovided for draining excess water from the second stage.' A' pressurefan 90 is disposed in the chamber downstream-of the second stage, andadjacent the inlet end of the third stage. in the casing.

A cooling coil 91 is disposed in the third stage,'having an inlet pipe92 and outlet pipe 93 connected thereto. A pump 94 is disposed in pipe92 for supplying coolant to the coil, while outlet pipe is connected toheader 88 to supply. the heated water to the spray nozzles in the secondstage. If desired, the cooling coil can be a refrigeration unit, inwhich case the water in pipe 92 can go directly to the spray header.Pipe 99 is an alternate direct source of supply of sea water to thespray header 88. A valve 100 is disposed in line 93 to shut off flowthrough it.

The spray nozzles are of a special commercial type called fog nozzleswhich produce a very fine mist composed of pure water vapor and veryfine droplets. Where fog nozzles are used instead of wick plates the fogshould be directed back against the inflowing air stream so that the aircan pick up the vapor and the droplets have time to fall to a pan at thebase before the air reaches the third stage. Any contamination in thewater does not pass to the vapor but it does to the droplets so that itis important that the droplets do not enter the third stage. Baffleplates 101 insure that the droplets do not enter the third stage.

A throttle valve of the butterfly type is disposed adjacent the outletfrom the third stage and can be controlled to give a predeterminedpressure differential. Product water is removed through pipe line 96 inthe third stage to a storage tank 97. Thus, with this embodiment thefirst stage can be utilized to heat air and reduce the pressure therein,while the third stage can be utilized to cool the air and increase thepressure of air vapor to abstract product water.

What is claimed is:

1. A "flotation and rotatable apparatus for producing potable watercomprising a frame, a ballast means carried by said frame, a looped airconveying duct secured to said frame having a substantially horizontalupper inlet section with an inlet end and a water reservoir therein, aplurality of wick members extending into said reservoir and disposedacross the .air flow path through said horizontal section, solar heatingmeans secured by said horizontal section, said duct having a downwardlycurved section connected at its inlet end to the outlet end of saidhorizontal section and communicating at its outlet end with asubstantially horizontally extending lower duct section, forced draftfan means disposed in said duct adjacent said curved and lower sectionsto decrease the pressure in-said upper inlet and curved sections and toincrease the pressure in said lower section, cooling coil means disposedin said lower section to condense out of the air stream water vaporcarried therein, an upwardly curved duct section communicating at itsinlet end with the outlet end of said lower duct section and disposedopposite said downwardly curved section and having its discharge openingfacing in a direction opposite to that j of the inlet end of said inletduct section and disposed vertically adjacent and below said inlet ductsection, a fresh water storage tank, means for passing condensed waterfrom said lower duct section to said tank, means for feedingcooling'water from said cooling coil means to said water reservoir, andrudder means for causing the inlet end of said inlet'duct section topoint into the wind, said ballast means being of suflicientdimension andsize to float said apparatus partially submersed in a body of water,and'means' for connecting an anchor to said apparatus.

2. A rotatable apparatus for producing potable water comprising firstand second substantially vertical cylinders with the. first cylinderbeing concentrically disposed within the second cylinder to provide anannular 'air flow passage therearoun'd, said second cylinder bei'ngfaclosed container and having an air inlet in the bottom thereof, saidfirst cylinder having a lower end section extending through said secondcylinder toprovide adis'charge outlet, the upper end of said firstcylinder being open' and spaced below the upper end of said secondcylinder to receive air therefrom, solar heating means disposed aroundthe outer surface ofsaid second'cylinder to heat air flowingtherethrough; forced 'dra'ft' fan' means to cause air to flow throughsaid first and second cylinders, an annular water reservoir in saidannular passage, with means extending into said reservoir and across thepath of flow of air in said annular passage toincrease the amount ofwater vapor carried in air flowing to said first cylinder, cooling meansdisposed in said first cylinder below said fan means to cool air causedto flow therethrough to condense water vapor in the air passingtherethrough, rotatable base support means for said first and secondcylinders, rudder means secured to said second cylinder to cause saidsecond cylinder air inlet to face into the wind, and means for supplyingfeed water to said water reservoir.

3. The apparatus of claim 2 wherein casing means composed of clearplastic enclose said solar heating means to prevent solar heat loss dueto wind, and auxiliary heating means are provided adjacent said secondcylinder air inlet.

4. An apparatus for producing potable water comprising a horizontalcasing having an inlet and outlet forming three stages therein, heatingmeans disposed adjacent said inlet to heat air caused to flowtherethrough, water spray means in said casing downstream of saidheating means for intercepting a stream of air passing therethrough toincrease the water vapor content of said stream of air, fan meansdisposed in said casing downstream of said spray means, indirect coolingmeans disposed in said casing downstream of said fan means for coolingsaid air stream, throttle valve means disposed in said casing downstreamof said cooling means to provide a predetermined pressure differentialin said casing between the inlet an-d outlet of said casing, and meansfor supplying water to said cooling means and spray means, and means fordischarging potable water from said casing.

5. The apparatus of claim 4 wherein said means for supplying water isconnected to said spray means in series therewith.

6. An apparatus for producing potable water comprising a structureincluding a first chamber having an inlet and outlet for passing ast-ream of air therethrough, means for heating the air stream in saidfirst chamber, a second chamber having an outlet and in communicationwith said first chamber outlet to receive the air stream therefrom,means for exposing said air stream to water vapor in said secondchamber, a third chamber in communication with the outlet of said secondchamber, means for flowing air through said chambers, means for coolingthe air stream passing through the third chamber to condense out watervapor carried in said air stream, said first, second, and third chambersbeing formed by substantially vertical cylindrical members, with theinnermost member disposed concentrically within an inter-mediate memberand said latter member defining an annular passage around said innermostmember to define said first chamber, base means upon which saidstructure is rotatably supported, and rudder means provided for saidstructure whereby said structure will always face into the wind.

7. An apparatus for producing potable water comprising a structureincluding a first chamber having an inlet and outlet for passing astream of air therethrough, solar heating means and means for reducingthe pressure of the air stream passing through said chamber to raise thedew point thereof, a second chamber in communication with said firstchamber outlet, means for charging said air stream in said secondchamber with the maximum amount of water vapor it will hold includingwick members and a reservoir provided in said first chamber, a thirdchamber in communicating with said second chamber to receive the airstream therefrom, said means for reducing the pressure in said firstchamber being operable to increase the pressure in said third chamber,and means for cooling the saturated air stream passing through saidthird chamber to condense water out of said air stream.

8. An apparatus for producing potable water comprising a structureincluding a first chamber having an inlet and outlet 'for passing astream of air therethrough, solar heating means for raising thetemperature and means for controlling the pressure of the air streampassing through said chamber to raise the dew point thereof, a secondchamber in communication with said first chamber outlet, means in saidsecond chamber including wick members "for charging said air stream withthe maximum amount of water vapor it will hold, a third chamber incommunication with said second chamber to receive the air streamtherefrom, said means for controlling the pressure in said first chamberbeing operable to increase the pressure in said third chamber, and meansfor cooling the saturated air stream passing through said third chamberto condense water out of said air stream, said means for controlling thepressure of the air stream including a fan and a throttle valve.

9. An apparatus as defined in claim 8 wherein said throttle valve ispositioned adjacent the outlet of said third stage and said fan ispositioned between said second and third stages.

10. An apparatus comprising an air duct having an inlet and an outletthrough which air flows, heating means for raising the capacity of theflowing air to absorb additional water vapor, means for exposing theflowing air to water vapor, cooling means for lowering the capacity ofthe flowing air to retain water and thereby condense water on surfacesfrom which it may be removed for use, a base member upon which said airduct is rotatably supported, and a vane responsive to wind for rotatingsaid air duct so that the inlet of said duct faces into the wind.

11. An apparatus as defined in claim 10 wherein a forced draft fan isdisposed in said air duct.

12. A flotation apparatus comprising an air duct having an inlet and anoutlet through which air flows, heating means for raising the capacityof the flowing air to absorb additional water vapor, means for exposingthe flowing air to water vapor, cooling means 'for lowering the capacityof the flowing air to retain water and thereby condense water onsurfaces from which it may be removed for use, floating means adapted tofloat on water and upon which said air duct is mounted, and a vaneresponsive to wind for moving said floating means on the water so thatthe inlet of saidduct faces into the wind.

References Cited UNITED STATES PATENTS 614,776 11/1898 Stocker 202-163804,973 11/ 1905 Poplawski 122-366 983,424 2/1911 Brosius 203-10 X1,516,225 11/1924 Webb 203- X 2,076,498 4/1937 Farwell 159-13 X2,332,294 10/ 1943 Bohmfalk 202-234 2,803,591 8/19 57- Coanda et al202-234 3,165,452 1/ 1965 Williams 202- X 3,248,3-06 4/ 1966 Cummings202-234 X FOREIGN PATENTS 780,272 7/ 1957 Great Britain.

NORMAN YUDKOFF, Primary Examiner.

J. SOFER, Assistant Examiner.

1. A FLOTATION AND ROTATABLE APPARATUS FOR PRODUCING POTABLE WATERCOMPRISING A FRAME, A BALLAST MEANS CARRIED BY SAID FRAME, A LOOPED AIRCONVEYING DUCT SECURED TO SAID FRAME HAVING A SUBSTANTIALLY HORIZONTALUPPER INLET SECTION WITH AN INLET END AND A WATER RESERVOIR THEREIN, APLURALITY OF WICK MEMBERS EXTENDING INTO SAID RESERVOIR AND DISPOSEDACRESS THE AIR FLOW PATH THROUGH SAID HORIZONTAL SECTION, SOLAR HEATINGMEANS SECURED BY SAID HORIZONTAL SECTION, SAID DUCTHAVING A DOWNWARDLYCURVED SECTION CONNECTED AT ITS INLET END TO THE OUTLET END OF SAIDHORIZONTAL SECTION AND COMMUNICATING AT ITS OUTLET END WITH ASUBSTANTIALLY HORIZONTALLY EXTENDING LOWER DUCT SECTION, FORCED TO DRAFTFAN MEANS DISPOSED IN SAID DUCT ADJACENT SAID CURVED AND LOWER SECTIONSTO DECREASE THE PRESSURE IN SAID UPPER INLET AND CURVED SECTIONS AND TOINCREASE THE PRESSURE IN SAID LOWER SECTION, COOLING COIL MEANS DISPOSEDIN SAID LOWER SECTION TO CONDENSE OUT OF THE AIR STREAM WATER VAPORCARRIED THEREIN, AN UPWARDLY CURVED DUCT SECTION COMMUNICATING AT ITSINLET END WITH THE OUTLET END OF SAID LOWER DUCT SECTION AND DISPOSEDOPPOSITE SAID DOWNWARDLY CURVED SECTION AND HAVING ITS DISCHARGE OPENINGFACING IN A DIRECTION OPPOSITE TO THAT OF THE INLET END OF SAID INLETDUCT SECTION AND DISPOSED VERTICALLY ADJACENT AND BELOW SAID INLET DUCTSECTION, A FRESH WATER STORAGE TANK, MEANS FOR PASSING CONDENSED WATERFROM SAID LOWER DUCT SECTION TO SAID TANK, MEANS FOR FEEDING COOLINGWATER FROM SAID COOLING COIL MEANS TO SAID WATER RESERVOIR, AND RUDDERMEANS FOR CAUSING THE INLET END OF SAID INLET DUCT SECTION TO POINT INTOTHE WIND, SAID BALLAST MEANS BEING SUFFICIENT DIMENSION AND SIZE TOFLOAT SAID APPARATUS PARTIALLY SUBMERSED IN A BODY OF WATER, AND MEANSFOR CONNECTING AN ANCHOR TO SAID APPARATUS.